Numerous compositions have been proposed for the electrodeposition of palladium, and various electrolytes have been utilized to provide sufficient conductivity in such compositions. Cyanide baths for plating many of the noble metals have found considerable commercial application; however, there are of course pollution problems attendant to such baths, which have created an increasing trend toward the substitution of other electrolytes.
As is true with many of the noble metals, small amounts of brighteners may be employed in palladium baths to achieve optimum specular brightness in the eletrodeposit. Although highly effective and desirable from that standpoint, there is sometimes a tendency for the brightener itself to reduce the ductility of the deposit or to reduce its adhesion to the substrate.
A composition and method for producing bright electrodeposits of palladium, while avoiding the pollution problems associated with the use of a cyanide electrolyte, are described and claimed in Skomoroski et al. U.S. Pat. No. 3,925,170, entitled METHOD AND COMPOSITION FOR PRODUCING BRIGHT PALLADIUM ELECTRODEPOSITIONS, which issued on Dec. 9, 1975. While being entirely satisfactory in most respects, the composition of the aboveidentified patent utilizes cobalt, nickel or a mixture thereof as the brightening agent, and the presence of a metal in the bath may be undesirable in certain instances, such as when a deposit of utmost purity is to be produced. Thus, it is desirable to provide a palladium electroplating composition which need not contain any metallic brightener.
Accordingly, it is an object of the present invention to provide a novel composition for the electrodeposition of palladium in bright, highly adherent coatings upon various types of conductive substrates.
It is a more specific object to provide such a composition which need not contain any metallic brightener.
It is also an object to provide such composition which is operble over a wide range of current density and at ambient to low elevated temperatures.
Another object is to provide a novel method for the electroplating of palladium which is relatively trouble free and relatively insensitive to minor variations in operating conditions, and which will produce bright, highly adherent electrodeposits of palladium.